This invention relates generally to an electrical connector and, more particularly, to a zero insertion force electrical connector having cam means therein for actuating the contacts out of engagement with conductors on an electrical component.
It is well known in the art that substantial force is required to insert a printed circuit board into a connector having a large number of spring contacts therein due to the resilient engaging force of the contacts with the edge of the board. As the number of contacts is increased in a connector, the amount of force required to insert the printed circuit board into the connector, or to withdraw it from the connector, may become excessive for practical use. In addition, direct insertion of boards into connectors having spring contacts therein results in a wiping action occurring between the contacts and the conductive traces on the edge of the board, which may cause excessive wear of the traces over lengthy periods of use of the connector. It is, therefore, a common practice in the art to provide a zero insertion force printed circuit board connector in which the contacts are mounted out of the path of movement of the board when it is inserted into the connector whereby no resistance is encountered upon inserting the board thereinto.
There are two general types of zero insertion force connectors, one in which the contacts are normally closed and the other in which the contacts are normally open. In the case of a connector having normally open contacts, the contacts are normally unloaded (that is, no stresses are applied to the contacts) and the contacts are cammed against the printed circuit board. In a connector having normally closed contacts, the contacts are preloaded in the connector housing in a position to resiliently engage a printed circuit board mounted therein and a cam actuator is provided for retracting the contacts away from the standard engagement position so that a board may be inserted into the housing with zero insertion force. The present invention relates to a zero insertion force connector having normally closed contacts.
In copending application of J. W. Anhalt, Ser. No. 866,031, filed Dec. 30, 1977, now U.S. Pat. No. 4,159,861, issued July 3, 1979, assigned to the assignee of the present application, there is disclosed a normally closed zero insertion force, printed circuit board connector comprising an elongated insulative housing having a row of contacts therein. The housing has a slot opening to the top for receiving the printed circuit board. Each contact has a mounting portion and a spring contacting portion which extends upwardly from the mounting portion at an angle in one direction toward a vertical plane passing through the opening in the housing. An arm on the spring contacting portion of each contact extends downwardly at an angle in a direction away from said vertical plane. Means is provided for retracting the contacting portions of the contacts away from the vertical plane. The retracting means includes a contact shifting element and a cam actuator. The contacting shifting element is disposed between the spring contacting portions and the downwardly extending arms on the contacts. The contacting shifting element is movable vertically between a lower position and an upper position, and embodies a cam surface which engages the arms on the contacts for retracting the contacting portions of the contacts away from the vertical plane when the contacting shifting element is moved from its lower position to its upper position. The cam actuator is operated in one direction to move the contact shifting element from the lower position to the upper position to open the contacts so that a printed circuit board may be inserted into the housing with zero insertion force.
After the board is inserted into the slot, the cam actuator is operated in the opposite direction whereupon the contact shifting element returns to its lower position under the spring bias of the downwardly extending arms of the contacts. However, when the connector is subjected to vibration or shock, the contact shifting element may move vertically. The resulting inertial forces of the moving element are sometimes transferred to the contacts, thus causing contact vibration and possible intermittance in electrical engagement with the printed circuit board.
Copending application of B. K. Arnold, Ser. No. 894,934, filed Apr. 10, 1978, now U.S. Pat. No. 4,159,154, issued June 26, 1979, assigned to the assignee of the present application, discloses a solution to the foregoing problem of contact vibration, namely, the provision of latching means for restricting movement of the contact shifting element to its upper position except during operation of the cam actuator to open the contacts. Such latching means comprises interlocking teeth on the contact shifting element and the cam actuator. However, it has been found that due to excessive friction between the contact shifting element and the connector housing, engagement and positive locking of the teeth is not consistently attained. The object of the present invention is to overcome this problem.